Dust Deposition on Snow

Welcome to the Dust Deposition on Snow section of SDSG

Here you will find an assortment of information pertaining to the occurrences of dust-on-snow. This is not a source of original material but rather a combination of excerpts from scientific and popular press articles as well as a portal to a plethora of valuable information. None of the scientists mentioned are affiliated in any manner with SDSG. Their work is merely being referenced. Our goal is to provide a “one-stop-shop” for all relevant material dealing with dust and snow. We emphasize information related to the area in which we are located, the state of Colorado.

introduction

What are the dust events?

The Colorado plateau region - credit to nps.gov

Dust deposition on the mountains of Colorado has received growing attention over the past several years. While these events are not new occurrences, they have only been extensively studied for the past 20+ years. The issue is large plumes of dust that are carried predominantly from the Colorado Plateau region, an area spanning the Four Corners region of the western United States, and deposited onto the mountain ranges throughout the state.

While the origins of the dust storms have been determined, the exact cause or causes have not been scientifically identified. These dust events not only cause a decrease in the aesthetically pleasing views of the Colorado landscape, but they have distressing implications to the ecosystems, economies, and social aspects of the affected areas.

Why is the dust an issue?

The deposited dust drastically reduces the albedo, or reflectivity, of the snow. As a result, the snow absorbs more of the incoming solar radiation from the sun and thus melts quicker and sooner than a clean snowpack. This creates problems for the cities, industries, individuals, plants, and animals that rely on a slow-melting snowpack to provide them with water throughout the dry summer months. Instead, water is coming much sooner and more abundant than water managers are accustomed to. Although the dust storms are not the only contributing factor to earlier snowmelt, they are certainly a major catalyst for the snow to melt sooner.

The dust events exacerbate a growing problem in the western United States, earlier and more rapid snowmelt. This has implications for the concept of sustainability because it puts growing stress on the environment and people that rely on the water for a plethora of reasons.

The issue of dust deposition is not only an ecological issue but it also has implications to the strength and productivity of the livelihoods of people living in the Colorado River Basin. The Colorado River provides water to 40 million people in seven western states and two countries and irrigates 5.5 million acres of land (Deems et. al, 2013). The main water source of the Colorado River comes from alpine mountain areas (Deems et. al, 2013). The river has long been over-allocated and the occurrence of increased dust deposition is heightening the issues of water scarcity (Deems et. al, 2013). Decreased snow albedo from anthropogenic dust loading to the Colorado Mountains has shortened the duration of snowpack by several weeks relative to conditions prior to western expansion (Deems et. al, 2013). Dust from the Colorado Plateau has shortened the snow cover durations at high alpine sites by 25-50 days (Painter et. al, 2007). The most extreme projections of dust loading predict the reduction of 1% of the Colorado River’s annual flow volume (Deems et. al, 2013).

For example, farmers rely on continuous water flows throughout the summer to irrigate their crops. Ranchers depend on the availability of water to keep their animals healthy and hydrated. Ski areas need a clean, aesthetically pleasing spring snowpack on which people can ski. With the severity and frequency of dust events increasing during the past several years, the ability for future water users to meet their needs during the arid summer months may be more of an issue than once expected. In fact, the number of dust storms has varied with an overall increase since they have been monitored.

total dust on snow events 2004 - 2017

Above is a graph displaying the number of dust events since Total Dust-on-Snow Events (wet and dry dust events) in the Senator Beck Basin Study Area, San Juan Mountains, CO.

What Are Differences Between Wet & Dry Dust Events?

There are two types of dust deposition that affect the snowpack in Colorado. Wet deposition which is the input of nutrient in an ecosystem in a dissolved state. Wet deposition usually occurs through rainfall in most systems but in the case of dust deposition transportation in the mountains of Colorado, snow is the leading source of wet deposition.

Dry deposition is the variable form of dust deposition to occurring the mountains of Colorado from year to year as seen on the graph display above, Total Dust-on-Snow Events (wet and dry dust events) in the Senator Beck Basin Study Area, San Juan Mountains, CO. Dry deposition is an input of nutrients in an ecosystem in the particulate state. It usually occurs through dust foil and in the case of the mountains of Colorado is the typical form on deposition.

What Is Exactly Dust Deposition?

Dust is small, dry, solid particles projected into the air by natural forces such as volcanic eruption and wind. Dust can also be projected into the air through mechanical or man-made processes such as milling, drilling, conveying, bagging, sweeping, and demolition (IUPC, 1990). Dust particles vary in size but are usually between 1 to 100 micrometers in diameter (IUPC, 1990). Particles larger than PM10 dominate total atmosphere particle loads are not measured and this size particle would include the fine particulate matter of dust deposition (Brahney et. al, 2013). Presently, desert dust particles or dust deposition are not measured by the National Atmospheric Deposition Program on a regular basis. Also, measurements of total particle concentrations in southeastern Utah and western Colorado are not regularly measured (Brahney et. al, 2013).

Who are some of the leading scientists & institutions conducting research?

Points of Impact

The dust emanating from the Colorado Plateau region is deposited across the state of Colorado. While the dust events are heavily studied in the San Juan Mountains, they have been shown to deposit dust near Denver mountain ranges. Although significantly farther from the Colorado Plateau region than the San Juans, the dust events occurring nearer to Denver are just as severe as those which occur nearer the source area (Best, 2008). In 2009, which received a record total of 12 significant dust events since records began being kept in 2003, dust was found across the state following each event (Colorado Daily Staff, 2009).

Effects on Snow

Dust deposited on snow greatly reduces the snow’s ability to reflect the sun’s incoming solar radiation. Normally snow has the highest reflective properties of any natural substance on Earth (Painter et al., 2007). As shown in Figure 1 below, clean snow reflects 80-100% of incoming visible light. However, once dust has been deposited on the snow surface, the snow only reflects 50-60% of incoming visible light.

Figure 1 displays the reflective difference between clean and dirty (dust-laden) snow in the San Juan Mountains of Colorado–Taken from the presentation “How desert dust is influencing Colorado snowmelt” by Landry, Painter, and Barrett

Decreasing the albedo of the snow, thus increasing the absorption of solar radiation, causes the snow to melt at an unnaturally high rate. In 2006, dust-laden alpine snowpack melted up to 35 days sooner than a clean snowpack (Painter et al., 2007). In 2009, dust events led to the snowpack melting nearly 50 days sooner than a clean snowpack (Berwyn, 2009).

Figure 2 displays the San Juan Mountains on April 12, 2005 and April 12, 2006 respectively. The 2006 image shows a reduction in the snowpack’s spatial extent compared to the 2005 image–Courtesy of NASA

On the right are two images (Figure 2) displaying the San Juan Mountains. The first image was taken on April 12, 2005, after four dust events, via the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite. The second image was taken on April 12, 2006, after eight dust events, via MODIS on NASA’s Terra satellite. Comparing the two images, one can see evidence the snowpack in 2006, which had double the amount of dust events, had a much smaller spatial extent than at the same time in 2005. The abundance of dust as well as weather conditions (e.g. minimal cloud cover) allowed the snowpack to receive ample sunlight and melt at a quicker pace (Dust Reduces Snow Cover in the San Juans, 2007)

“Frequency of dust deposition and radiative forcing doubled when the Colorado Plateau, the dust source region, experienced intense drought (8 events and 39-59 Watts per square meter in 2006) versus a year with near normal precipitation (4 events and 17-34 Watts per square meter in 2005)” (Painter et al., 2007).

Impacts for Skiers

The dust not only causes the snow to melt quicker, but it creates unfavorable conditions for recreational use. The owner of Pine Needle Mountaineering in Durango, CO, Keith Roush, is quoted saying, “we haven’t skied as much this spring [2009], because the dust stops you dead in your tracks. It slows you down and throws you off balance. It’s like hitting sand” (Colorado Daily Staff, 2009). Lisa Branner of Venture Snowboards in Silverton, CO has said “the dust is definitely trashing the snowpack causing it to heat up, rot out and melt faster — shortening what could have been a great spring touring season” (Huffman, 2010). Chris Landry, one of the leading scientists studying the effects of dust deposition on snow, has said, “the last several years have been very disappointing as a skier, especially last year [2009] when you were, in effect, trying to ski on mud. It’s no fun” (Huffman, 2010).

Biological Impacts

“Seasonal snow cover has a substantial effect on ecosystem function where freezing temperatures over winter facilitate the formation and retention of a snow pack. It protects and sustains plant and soil communities by moderating temperatures during winter and later by supplying a source of water to fuel plant growth at the start of the growing season. The timing of snowmelt also regulates the timing of early season phenological events [flowering and growing] and can affect reproductive output” (Steltzer et al., 2009).

“In an alpine basin in the San Juan Mountains, the researchers [Steltzer et al.] simulated dust effects on snowmelt in experimental plots. They measured dust’s acceleration of snowmelt on the life cycles of alpine plants. The timing of snowmelt signals to mountain plants that it’s time to start growing and flowering. When dust causes early snowmelt, plant growth does not necessarily begin soon after the snow is gone” (NSF, 2009).

When dust deposition causes snowpack to melt sooner, plant activity is postponed until ambient air temperatures have warmed to above freezing temperatures. Dr. Heidi Steltzer, a biology professor at Fort Lewis College has said, “Climate warming could therefore have a greater effect on the timing of growth and flowering” (O’Donoghue, 2009). Futhermore, Dr. Steltzer stated, “Desert dust alters the ecology of alpine landscapes from staggered to more synchronized plant growth. With increasing dust deposition from drying and warming in the deserts under global warming, the composition of alpine meadows could change as some species increase in abundance, while others are lost, possibly forever”(NSF, 2009). The synchronization of plants also “…could increase nutrient losses to aquatic ecosystems before greening and alter species interactions” (Steltzer et al., 2009).

Lastly, Steltzer et al. (2009) concluded:

“Synchronized life histories across a landscape could decrease nutrient retention by reducing temporal variation in nutrient demand among topographic positions. In particular, delayed phenology after snowmelt would postpone plant demand for resources, leading to decreased nutrient retention when nutrient availability is high. During the growing season, concurrent growth and flowering across the landscape could alter species interactions, increasing competition for limiting resources and pollinators and changing landscape-scale gene flow via pollination. Decreased spatial variation in plant phenology can also reduce foraging success by large herbivores with consequences for offspring production. Thus, the atmospheric transport of desert dust is a process that links human activities in desert ecosystems to changes in phenology in alpine landscapes, which could affect biotic interactions and nutrient cycling by synchronizing phenology across the tundra.”

Implications of Earlier Snowmelt

“If the shifts in snowmelt timing…continue, they have important implications for reservoir operation and flood risk, water rights, wildfire severity, and forest ecology in Colorado. Snowmelt will occur earlier, but the runoff season may increase in length, which could reduce the risk of flooding during snowmelt. On the other hand, flood risk might increase if warming temperatures cause Colorado to experience more rain-on-snow events, which have been relatively uncommon in the state compared to the Pacific Northwest. Changes in snowmelt timing may affect water rights whose seniority varies with time of year. Stakeholders whose water rights are senior late in the year, but are more junior early in the year, may be losers under scenarios of increased springtime warming. Earlier snowmelt may cause soil moisture to decline during summer, increasing drought stress in trees, making them more susceptible to wildfires and insect infestation” (Clow, 2009).

In a study conducted by Tim Barnett of the Scripps Institution of Oceanography to research the effect climate change could potentially have on water resources in the western U.S., they found:

“Even by mid-century we see that the Colorado River Reservoir System will not be able to meet all of the demands placed on it, including water supply for Southern California and the inland Southwest, since reservoirs levels will be reduced by over one-third and releases reduced by as much as 17%. The greatest effects will be on lower Colorado River Basin states. All users of Colorado River hydroelectric power will be affected by lower reservoir levels and flows, which will result in reductions in hydropower generation by as much as 40%. Basically, we found the fully allocated Colorado system to be at the brink of failure, wherein virtually any reduction in precipitation over the Basin, either natural or anthropogenic, will lead to the failure to meet mandated allocations” (Barnett et al., 2004).

Earlier snowmelt affects ranchers and farmers who depend on a slow-melting snowpack to provide them with water throughout the summer (Streater, 2009).

“Colorado — which is under an agreement with the Bureau of Reclamation to divert roughly 38 million gallons a year from the San Juan River Basin to thirsty cities in New Mexico, including Albuquerque and Santa Fe — now fears it may not be able to meet the terms of the water transfer agreement as the snow melt arrives early and flows downstream” (O’Donoghue, 2009).

Effects on Ecosystems

“Eolian dust mobilized from arid-land soils generally contains high concentrations of base cations, and dust typically has high concentrations of N [nitrogen] and P [phosphorus], as well as elevated concentrations of a range of atmospheric pollutants. High-elevation lakes and tundra ecosystems are generally low in nutrient content and vulnerable to increases in atmospheric deposition. There is strong evidence for the impacts of changing N deposition in high-elevation settings, as well as suggestions of increasing P and base-cation deposition into high-elevation settings” (Neff et al., 2008).

“There is evidence from a range of other settings that base-cation loading via dust deposition can change precipitation and surface-water alkalinity. The relatively large perturbation to base-cation loading to these lakes suggests that dust inputs could be one factor mitigating the lake impacts of generalized regional increases in acid deposition” (Neff et al., 2008).

“Dust inputs can alter soil fertility significantly and thus affect many ecosystem properties, including plant-community composition and productivity. As soils age, the supply of soil nutrients from minerals declines unless replaced by other inputs, such as dust. Dust may contain not only many plant-essential nutrients (e.g., Na, P, K, and Mg), but also substances that affect the availability of these nutrients (e.g., carbonates). P, which is commonly a limiting nutrient in desert soils, can govern plant productivity as well as affect carbon and nitrogen mineralization rates in deserts. K and Mg may strongly influence plant-community composition in semiarid areas. Even small increases in the proportion of fine particles, or in some nutrients, may increase invasibility by exotic annual plants” (Reynolds et al., 2001).

“The future nutrient load in the soils of the central Colorado Plateau thus depends on the balance of nutrients lost and regained, as well as composition of future dust inputs, all of which will be influenced by climatic variability and human activity as they modify southwestern landscapes” (Reynolds et al., 2001).

“…CU-Boulder researchers have observed increased algal growth in streams and lakes as a result of rising nitrogen deposition, as well as changes in the composition and diversity of wildflowers on the tundra. “Because these types of inputs have the potential to increase plant growth, the ultimate outcome of such depositions could change the fabric of our ecosystems,” said Neff” (EurekAlert, 2008).

Points of Origin

“Dust deposition on mountain snow cover has occurred throughout much of recent history as demonstrated by annual dust layers in high elevation ice cores, increasing with prolonged or intense drought and land disturbance in source regions” (Painter et al., 2007).

“The Great Basin, Colorado Plateau, Mojave, and Sonoran deserts of the southwestern United States are responsible for the majority of [dust] emissions in North America” (Neff et al., 2008).

“According to anecdotal evidence, historical research, and recent observations…the San Juan Mountains receive multiple dust deposition events annually in February through May, arriving before and during the snowmelt period” (Painter et al., 2007).

“There are a number of potential sources of dust to the San Juan Mountains including the deserts of the southwestern United States and desert sources in Asia that are known to contribute dust to the North American continent. Although the precise provenance of San Juan dust samples is difficult to determine, the physical and isotopic properties of dust can be used to substantially narrow the potential source regions” (Neff et al., 2008).

How do we know?

After testing, “these isotopic compositions are consistent with dust sources to the south and/or southwest of the study area. Satellite detection of dust plumes and atmospheric back-trajectory modeling for this region also link wintertime dust deposition in the San Juan Mountains to dust plumes that originate in the deserts of the southwestern United States, further supporting a dust source indigenous to western North America” (Neff et al., 2008).

Trajectory analyses show a majority of dust storms emanating from the CO Plateau Region–Taken from the presentation “Radiative effects of desert dust deposits in alpine snow” by Dr. Tom Painter

“Although Asian dust periodically falls on the San Juan Mountains, the textural distribution of dust samples also provides strong evidence for a regional source of dust. Nearly 40% of the mass of dust sampled from the snowpack occurs in the 10-37 µm size class, 26% in the 37-63 µm size class and 17% in the 63-180 µm size class. The relatively large proportion of particles over 37 µm is evidence for particles that have been transported hundreds, rather than thousands, of kilometers. This result suggests that the dominant source of wintertime dust inputs to the San Juan Mountains is the western United States rather than far-traveled Asian dust, which would be much finer (that is, in the less than 10 µm size classes)” (Neff et al., 2008).

“With the exception of a single event with northwesterly flow (February 22, 2003) across southeast Utah, the remaining events had southwesterly flow across northeastern Arizona and northwestern New Mexico” (Painter et al., 2007).

“The researchers found that the dust affecting San Juan snow cover came not from the immediate vicinity but from the Colorado Plateau, including the Four Corners region where the borders of Utah, Colorado, New Mexico, and Arizona intersect. Since the late nineteenth century, the American Southwest has seen significant land-use changes, including the expansion of grazing, recreational use, and agriculture. These land-use changes have disturbed desert soils and increased windblown dust” (Dust Reduces Snow Cover in the San Juans, 2007).Characteristics of Source Area

Characteristics of a Source Area

“The erosivity of the soil surface, and thus the potential impacts of aeolian [wind-driven] processes at the plant-interspace scale, depend on both the ability of the soil surface to resist erosion and the ability of the wind to reach the soil surface. Erosion resistance is determined by the strength of the soil and presence of surface protectors, such as rocks, plant litter, and physical and biological soil crusts. Rocks and plant litter too large to be moved by wind offer the greatest soil protection. Physical soil crusts – created by the binding together of silt and clay particles when wetted and then dried – protect soils, except when crusts are subjected to disturbance. Unless disturbed, these soils have an inherently higher resistance to erosion than soils dominated by coarser sand particles. Biological soil crusts, composed of cyanobacteria, lichens, and moss, stabilize soils by excreting mucilaginous material that binds soil surface particles together, thereby increasing soil aggregate size and increasing soil resistance to the shearing forces of wind” (Field et al., 2009).

Desert soil near Moab, Utah–Taken from the presentation “Utah BLM’s Role in Colorado’s Early Snowmelt” by SUWA

“The type, cover, and arrangement of vegetation have the strongest influence on the ability of the wind to reach the soil surface. The patchy and dynamic nature of vegetation in dryland regions results in aeolian transport being highly heterogeneous in both space and time. The amount of material that is moved depends on the size of unvegetated gaps upon which the wind can act (generally excluding rocky or gravelly areas, referred to as desert pavement, and areas covered by physical or biological soil crust) and the height and density of the vegetation, which controls the size of the protected area downwind of individual plants. Although surface characteristics are important, the amount of horizontal flux depends largely on the structure of the ecosystem and the degree of connectivity between unvegetated gaps” (Field et al., 2009).

Potential Causes of Dust Events

“Many of the factors that drive wind erosion are, of course, greatly affected by soil surface disturbances. Grazing cattle crush biological and physical soil crusts and decrease vegetative cover, thereby increasing wind erosion. Offroad vehicles and military training activities also crush vegetation and impact plant-interspace surface characteristics, particularly biological and physical soil crusts. Fire can dramatically increase wind erosion, although fire may be less spatially extensive than grazing and recreational use. Burning vegetation (even by typical rangeland fires) releases different amounts of organic compounds, which, in turn, lead to different levels of water repellency in the soil, depending on various factors, such as vegetation type, soil properties, and fire intensity and duration. Fire-induced water repellency decreases the strength of interparticle wet-bonding forces by increasing the soil-water contact angle. This repellency enhances soil erodibility by causing a drop in threshold friction velocity, thereby increasing post-fire erosion” (Field et al., 2009).

Offroading can break up the natural soil crust–Taken from the presentation “Utah BLM’s Role in Colorado’s Early Snowmelt” by SUWA

“…during settlement of the western U.S., the intensification of human activities such as agriculture, grazing, and resource exploration in semiarid landscapes led to 500% greater dust deposition in the adjacent mountains. Furthermore, dust deposition in many regions could increase as a result of the increasing extent of arid lands and greater human activity in these areas” (Steltzer et al., 2009).

“Expansion and intensification of grazing, recreational use and agriculture over the past ~140 years has increased the dust emission from the Colorado Plateau and other desert regions of the western US” (Painter et al., 2007).

Taken from the presentation “Dust in low elevation lands: what creates it and what can we do about it?” by Dr. Jayne Belnap et al.

“A change in dust source over the past several decades may result from the increasing disturbance of southwestern desert surfaces by human activities that include urbanization, agriculture, livestock grazing, off-road vehicle use, use of dirt roads, water diversion from lakes, and military training. These activities increase dust emission from previously stable desert surfaces” (Reynolds et al., 2001).

“…dust deposited in the San Juan Mountains comes primarily from the Colorado Plateau. Precipitation in the fall 2005/winter 2006 on the Colorado Plateau was the lowest on record and contributed to the doubling of the number of deposition events over those 2003-2005. We conclude then that snow cover duration across the San Juan Mountains is reduced by 18-35 days due to the deposition of dust from the disturbed deserts of the Colorado Plateau and not from sources local to the mountain basins” (Painter et al., 2007).

“More than 50% of the conterminous United States experienced moderate to severe drought conditions in 2002, with record or near-record precipitation deficits throughout the western United States” (Cook et al., 2004).

Energy exploration can destroy desert soils–Taken from the presentation “Utah BLM’s Role in Colorado’s Early Snowmelt” by SUWA

“Drought abated in many areas by late 2002 to early 2003, but severe drought conditions have continued to affect the interior western United States throughout the 2004 summer” (Cook et al., 2004).

Current Situation

“Twelve dust-on-snow events during the winter of 2008/2009 led to a 40 to 50 day earlier snowmelt–which occurred 20 days earlier than normal–with record streamflow rates” (Dybas, 2010).

A 2009 spring dust event blankets the sky–Courtesy of Jack Brauer

You can examine surface water data for the entire state of Colorado here: USGS Water Data. This link provides: real-time data, daily data, daily/monthly/annual statistics, peak-flow data, and field measurements for a number of surface waters across Colorado.

“Landry has documented “dust events” annually since 2002-03. The phenomenon is increasingly serious, but it’s way too early to show a trend, Landry said” (Rodebaugh, 2010).

Who is monitoring?

“Landry’s discussions with water managers led to the development of CODOS [Colorado Dust-on-Snow program], now funded by local, regional, state and federal water management agencies. CODOS monitors the statewide distribution of dust in mountain snow cover and reports on that distribution in biweekly advisories” (Dybas, 2010).

Options to curb the problem?

“Designating wilderness is one way to control these [land disturbing] factors, according to SUWA’s Martin. Wilderness automatically precludes off-highway vehicle travel, road building, and oil and gas drilling. Without these kinds of disturbance, SUWA [Southern Utah Wilderness Alliance] hopes that the frequency of dust storms will drop” (Sands, 2010).

“…SUWA and Great Old Broads are throwing cautious support behind a “fast-moving process” to dedicate up to 1.3 million acres of wilderness west of Durango. Utah Sen. Bob Bennett has initiated the process to protect huge swaths of Canyonlands and Cedar Mesa, including spots like Indian Creek, Dark Canyon and Grand Gulch. Bennett hopes to introduce legislation in June and have it adopted as a rider to the Ominbus Appropriations Bill in September. The senator is currently engaging stakeholders in Southeast Utah and asking for input on crafting a wilderness bill for the area” (Sands, 2010).

“Minimize invasion by annual grasses

Control N and S deposition (cars, power plants)

Reduce disturbance of susceptible soil

Study system resistance

Minimize dirt roads and their use

Minimize fertilizing (e.g., NPK, alfalfa) dryland soils, as annuals will dominate. If fields are abandoned, replant perennials” (Jayne Belnap, 9/18/2009 Dust in low elevation lands: what creates it and what can we do about it?).

Dust events have increased over the past several years

“Another spike has hit in recent years, and the size and frequency of dust storms appear to be on the rise again. “In the late 1800s, dust loading skyrocketed and was about five times as high as our background data,” Neff said. “Today, dust is about three or four times the background, and livestock, off-road vehicles, human development, dirt roads and weather are all factors” (Sands, 2010).

“A Washington Post analysis of federal data from areas managed by the Bureau of Land Management found that between 2004 and 2008, off-road vehicle use rose 19 percent, the number of oil and gas wells increased 24 percent and grazing acreage climbed 7 percent” (Eilperin, 2009).

Dust deposited on a car windshield–Courtesy of Jack Brauer

“Advocates for off-road vehicle users, for example, charge that environmentalists have seized upon the dust issue as a political club in their efforts to curb the increasingly popular recreational sport. “A lot of the public land in the West is a very dusty place. What human uses make it more dusty, and to what extent, is unknown,” said Brian Hawthorne, public lands policy director for the BlueRibbon Coalition, which represents off-road enthusiasts. “There’s just no studies on it” (Eilperin, 2009).

“The earlier snowmelt changes the blooming and growing times of vegetation, triggering ripple effects that hurt Colorado farmers. Steve Vandiver, general manager of the Rio Grande Water Conservation District, said farms in the valley are getting the snowmelt runoff two to four weeks earlier each year, making it difficult to keep grain and potato crops irrigated. “A lot of the water’s gone by the time the crops need it,” he said” (Eilperin, 2009).

“…Many Southwestern communities are struggling with poor air quality, and dust is making it worse. Arizona’s Maricopa County, which includes Phoenix and Scottsdale, has failed to meet federal air quality standards and is cracking down on off-road vehicles and unpaved roads to limit dust” (Eilperin, 2009).

“If grazing leads to disturbances of BSCs, regeneration typically requires decades for the initial colonization and hundreds of years for a crust lichen community to form. During this long regeneration period, wind erosion of exposed soils could increase” (Neff et al., 2005).

“While some regeneration of the lichen/moss component of the crusts is now occurring, this process takes several hundred years in these environments” (Neff et al., 2005).

Historical Information

Not a new phenomenon

“Dust deposition on mountain snow cover has occurred throughout much of recent history as demonstrated by annual dust layers in high elevation ice cores, increasing with prolonged or intense drought and land disturbance in source regions” (Painter et al., 2007).

A newspaper clipping from the January 27, 1950 edition of the “Silverton Standard” with a story about red dust deposits on snow–Taken from the presentation “Dust in the western US; a history of mineral aerosol deposition to Colorado” by Dr. Jason Neff

“Like many arid environments, the drylands of the western United States have experienced widespread land-use change over the past two centuries, with rapid acceleration of agricultural and grazing activities following the westward expansion of the United States in the 1800s. Despite growing evidence of the impacts of land use on wind erosion of soils around the world, the history of human influences on atmospheric dust remains poorly documented. Records showing increased dust accumulation in Antarctic ice cores between the nineteenth and twentieth centuries, and evidence for changing chemistry of glacial dust during the twentieth century, suggest higher contemporary atmospheric mineral aerosol loads than during the pre-industrial period” (Neff et al., 2008).

Although not a new issue, it has gotten worse since records have been kept

Dr. Jason Neff extracts sediment cores from Porphyry Lake in the San Juan Mountains of Colorado–Credit to Dan Fernandez

“By studying sediment cores from high-elevation lakes in the San Juan Mountains, Jason Neff, a geological sciences professor at the University of Colorado at Boulder, has estimated that the amount of dust falling back to Earth now is up to five times as much as the amount before Europeans arrived. Dust deposition was even greater around the turn of the last century, before the government put restrictions on grazing” (Eilperin, 2009).

“In two alpine lakes, sediment accumulation rates over the past ~150 yr are more than five times greater than average accumulation rates over the past 5,000 yr, on the basis of radiogenic 210Pb and 14C dates” (Neff et al., 2008).

“…the period of increased sedimentation rate is contemporaneous with an intensification of western US land use, and particularly livestock grazing activities, that began in the early 1800s” (Neff et al., 2008).

““From about 1860 to 1900, the dust deposition rates shot up so high that we initially thought there was a mistake in our data,” said Neff. “But the evidence clearly shows the western U.S. had it’s own Dust Bowl beginning in the 1800s when the railroads went in and cattle and sheep were introduced into the rangelands”” (EurekAlert, 2008).

“While droughts can trigger erosion and increased dust deposition, western U.S. droughts during the past two centuries have been relatively mild compared to droughts over the past 2,000 years, Neff said. Instead, the increased dustiness in the West coincides with intensive land use, primarily grazing, according to radiocarbon dating and lead isotope analysis of soil cores retrieved from lakebeds, he said” (EurekAlert, 2008).

“The study also shows more than a five-fold increase in nutrients and minerals in the lakebed sediments during the last 150 years, said Neff. Increases in nitrogen, phosphorus, potassium, calcium and magnesium – byproducts of ranching, mining, and agricultural activity – have been shown to change water alkalinity, aquatic productivity and nutrient cycling” (EurekAlert, 2008).

“Overall, nearly 70% of the natural ecosystems of the western United States have been affected by livestock grazing, resulting in loss of soil stability and increases in wind erosion of soil. The extensive degradation of western US rangelands led to the Taylor Grazing Act of 1934, which imposed regulations and restrictions on grazing activities in these rangelands. At about this time the mass accumulation rates of the lake sediments begin a moderate decline, which persists through the second half of the twentieth century” (Neff et al., 2008).

Implications for Sustainability

The following is a non-exhaustive list of implications to sustainability. This list covers possible issues arising from dust, dust deposition on snow, and earlier snowmelt.

Environmental Implications

The synchronization of plant growth creates an abundance of plant life at the beginning of the growing season. This creates competition among animal life and pollinators for limited resources (Steltzer et al., 2009).

Plant-eaters may find it more difficult to find an abundance of plant life throughout the summer months, affecting the possibility of reproduction (Steltzer et al., 2009).

Since nutrients in soil (eg nitrogen and phosphorus) are comparatively smaller than other material in soil, the nutrient content of the area where the dust is originating from will decrease while the nutrient content in areas where the dust is deposited will increase (Field et al., 2009).

“Dust decreases snow albedo, removing snow cover earlier and revealing a markedly darker land surface that absorbs solar radiation and reradiates in the infrared to the atmosphere. The triggering of earlier and faster snowmelt by dust can potentially result in less total and less late-season water supplies in areas where seasonal water scarcity occurs” (Field et al., 2009).

“In stable soil surfaces on the Colorado Plateau, dust accumulation in soils has increased the stocks of all macro- and micronutrients, especially phosphorus and magnesium” (Field et al., 2009).

“Even small increases in the proportion of fine particles, or in some nutrients, may increase invasibility by exotic annual plants” (Reynolds et al., 2001).

“Earlier snowmelt may cause soil moisture to decline during summer, increasing drought stress in trees, making them more susceptible to wildfires and insect infestation” (Clow, 2009).

“In the Niwot Ridge alpine region west of Boulder…CU-Boulder researchers have observed increased algal growth in streams and lakes as a result of rising nitrogen deposition, as well as changes in the composition and diversity of wildflowers on the tundra” (EurekAlert, 2008).

Economic Implications

Since the dust events degrade the recreational value of the snow, ski seasons may be cut short or interrupted and backcountry spring skiing is hindered.

“The dust is definitely trashing the snowpack,” says Lisa Branner of Silverton-based Venture Snowboards, “causing it to heat up, rot out and melt faster — shortening what could have been a great spring touring season” (Huffman, 2010)

Given that the runoff and peak flows occur earlier in the year, farmers may not receive enough water later in the summer months to irrigate their crops leading to less productivity (Riccardi, 2009).

“The closures on such a critical transportation artery have snarled freight and thrown delivery schedules into turmoil, said Karen Rasmussen, president of the Arizona Trucking Association” (Fuetsch, 2010).

“Over a period of six weeks this April and May, Interstate 40 was closed seven times between Winslow and Winona due to blowing dust that created gray-out conditions and toppled vehicles and signs. Last year, I-40 was closed five times” (Larmer, 2010).

“It’s also a big challenge for Colorado’s whitewater boating community and the industry credited with contributing $140 million annually to the state economy. A month earlier on the calendar, cold weather diminishes the appeal of river running. And stretching the season into warm summer months can become problematic after an early peak. Fishermen face similar problems as rivers warm and wane ahead of schedule” (Willoughby, 2010).

“The city’s [Aspen] water department has to spend more money in increased treatment chemicals to remove the dust, which resists coagulation. It makes its way through the city’s filters and is difficult to remove, according to city officials” (Sackariason, 2010).

“There are also broader implications as arid Western states wage costly legal battles over access to water supplies that are dwindling, in part, because of early snowmelt” (Streater, 2009).

Social Implications

“…the biggest impact is hydrologic. We’re seeing earlier and faster runoff, which makes it harder to manage resources. In the West, we depend on the snowpack as a reservoir. We can store a lot more water in the snowpack than in our surface reservoirs. If you melt everything off a month early and melt it off faster, that’s a big challenge for water managers” (Willoughby, 2010).

“Earlier snowmelt by desert dust depletes the natural water reservoirs of mountain snowpacks and in turn affects the delivery of water to urban and agricultural areas,” Painter said” (O’Donoghue, 2009).

“Arizona is ground zero for a nasty fungal infection called Valley Fever. People infected with the fever can be sick for weeks, or in more severe cases, half a year. The infection is specifically caused by spores carried in dust through the air. Cases spike during the Monsoon season” (Kuzj, 2010).

“Changes in snowmelt timing may affect water rights whose seniority varies with time of year. Stakeholders whose water rights are senior late in the year, but are more junior early in the year, may be losers under scenarios of increased springtime warming” (Clow, 2009).

“Blowing dust and brown-out conditions on Interstate 70 in eastern Colorado caused a massive traffic accident involving eight passenger cars and six tractor-trailer trucks, leaving two confirmed dead and multiple motorists with injuries, the Colorado State Patrol said this afternoon” (Pankratz, 2009).

Future Outlook

Some of the following scenarios are hypothetical in nature but should still be taken with merit as they reflect the possible future events and issues.

Return of the Dust Bowl times?

A giant dust storm approaches the town of Goodwell, OK during the Dust Bowl years–Credit to Chris Johns/National Geographic/Getty Images

“The dust storms are a harbinger of a broader phenomenon, researchers say, as global warming translates into less precipitation and a population boom intensifies the activities that are disturbing the dust in the first place. Jayne Belnap, a research ecologist at the U.S. Geological Survey who has studied the issue, predicts that by midcentury, the fragility of the region’s soil “will be equal to that of the Dust Bowl days,”” (Eilperin, 2009).

Global warming could exacerbate the problem

“Under global warming, increased drought is projected for the southwest US, Middle East, and the expanding Sahel. All of these deserts are known dust sources for winter and spring deposition to mountain snow cover in the Rocky Mountains, Central Asia, and the Alps, respectively” (Painter et al., 2007).

“Future drying in desert regions and projected expansion and intensification of use of arid and semi-arid lands could cause regional dust emission to increase in frequency and magnitude. Therefore, earlier snowmelt and its effects on mountain water resources and glacial extent is a likely scenario in many of the world’s mountain ranges under enhanced dust deposition” (Painter et al., 2007).

“By 2050, increased temperature alone is expected to decrease average soil moisture conditions in the southwestern US to levels below those experienced during the most severe droughts of this century, including the Dust Bowl years. Such declines in soil moisture will probably result in a reduction in the protective vegetative cover, a slower recovery from disturbance, and an increase in dust emission from exposed soil. Lower soil moisture will also mean drier fuels that burn more readily – wildfires in the western US are projected to increase substantially in both frequency and intensity, which will also increase exposed soils and the hydrophobicity of those soils, thus amplifying dust emissions” (Field et al., 2009).

Human activity “fueling the fire”

“An increase in human settlement/use of these landscapes will be accompanied by a further loss in the protective covering of plants, plant litter, and physical and biological soil crusts, thereby amplifying dust emissions from the disturbed surfaces. Offroad recreational activity in southern California has risen from virtually zero in 1960 to almost 10 million user-days in 2006. If users drive 32 km per day, this specific activity alone, in this relatively small region, can generate as much as 2.7 metric tons of dust per year. The now-exploding exploration and development of energy resources (including wind and solar) in dryland regions are also of concern. All of these activities will result in the loss of vegetation and soil surface protectors (eg scraping away vegetation for solar farms and oil pads), increased offroad vehicle traffic, pipelines, transmission lines, and greatly increased traffic on existing and newly established dirt roads” (Field et al., 2009).

“In summary, greater dust emissions, including more frequent and larger dust storms, are likely to occur from dryland regions as temperatures increase and more dryland areas are trampled, cleared of vegetation, plowed, and/or converted from perennial to annual plants” (Field et al., 2009).

Hurdles to overcome

“The overarching challenge for ecologists and other environmental scientists, land managers, and policy makers will be to work together to manage vulnerable areas in ways that reduce excess dust production to the fullest extent possible” (Field et al., 2009).

Innovative storm prediction techniques

“Researchers based at the University of Pittsburgh have developed a method for predicting dust and sandstorms that uses infrared satellite images to determine when conditions are ripe for the destructive phenomena, a technique that could be implemented globally and that the research team used to forecast a 2008 New Mexico dust storm — the area’s largest in decades — two days beforehand.

Thermal and visible images of New Mexico’s White Sands Dune Field captured by NASA’s Earth-orbiting ASTER (Advanced Spaceborne Thermal Emission and Reflectance Radiometer) instrument reliably indicated when soil moisture levels were low enough to result in a dust storm, the team recently reported in the Journal of Geophysical Research Earth Surface. Lead author Stephen Scheidt, a research associate in Pitt’s Department of Geology and Planetary Science; Michael Ramsey, a Pitt associate professor of geology and planetary science and member of NASA’s ASTER science team; and Nicholas Lancaster of Nevada’s Desert Research Institute further determined that this approach could be expanded into a worldwide system to monitor areas prone to dust storms or to track drought in regions threatened by desertification” (ScienceDaily, 2010).

Useful Links

The CSAS is one of the leading research institutions studying the dust-on-snow phenomenon. They are constantly monitoring the events and provide weekly updates to their funders on how the dust will impact the snow.

The USGS is committed to tracking the dust events via satellite imagery and ground measurements. Their primary objective is “to determine the location, size, frequency, duration, and transport patterns of dust storms in the southwestern United States.”

The USGS also has monitoring sites scattered across the nation measuring various aspects of water flows. Here you can select the site of choice and receive real-time and historical data for the water flow at that particular site.

The National Snow and Ice Data Center does extensive research on snow, ice, and climatology.

The NRCS has snow-monitoring sites (SNOTEL) scattered across Colorado. They also perform climate monitoring and water supply.

The Colorado Plateau Research Station at the USGS monitors and studies conditions in the Colorado Plateau region. Their main focus is “ecoregional studies and conservation planning; endangered species studies; vegetation distribution, ecology, and dynamics; data management and dissemination; inventory and monitoring studies; and wildlife ecology.”

The Institute of Arctic and Alpine Research “strives for excellence in research, education, and outreach related to Earth System Science and Global Change in high-latitude, alpine, and other environments.”